1. Field of the Invention
The present invention relates to an electron emission source composition and a method of producing an electron emission source for a flat panel display using the same, and, more particularly, to an electron emission source composition having an improved adherent strength with the substrate as well as stable and uniform electron emitting characteristics, and a method of producing an electron emission source for a flat panel display using the same.
2. Description of the Related Art
Earlier field emission displays (hereinafter referred to as “FED”) were made of a spindt-type electron emission source including Mo or Si, with sharp tips of sub-micron size. Since the spindt-type electron emission source is assembled in a sub-micron size, the method of fabricating the same requires a great deal of attention, and such an operation is considered high-level precision work. Thereby, it is difficult and expensive to produce a large-sized field emission display device.
Carbon material has recently emerged as a potentially useful electron emission source due to its low work function. One carbon material, a carbon nanotube (CNT), is particularly anticipated to be an ideal electron emission source since it features a high aspect ratio and a small tip radii of curvature of 100 Å, and thereby electrons are readily emitted by applying an external voltage of as low as 1˜3 V/μm.
Generally, the electron emission source is fabricated in a such manner that the carbon nanotube is formed in a paste with a solvent, a resin, and so on, and it is applied between substrates by a screen-printing method, then it is sintered. Since the carbon nanotube has a low work function, the resultant electron emission source can be driven by applying low voltages, and the method of fabricating the same is not complicated. It will thereby offer advantages to realize a large size panel display.
However, when the electron emission source is produced with carbon nanotubes by the screen-printing method, each carbon nanotube 1 is roughly mixed with a solid powder present in the paste, and the tips of most carbon nanotubes 1 are covered by the solid powder as shown in FIG. 5. Consequently, the electron emission capabilities are not fully utilized.
Therefore, there are considerable demands to find a way to expose the tips of the carbon nanotubes. As one scheme to satisfy such demands, Korean patent laid-open publication No. 2000-74609 discloses that carbon nanotubes are admixed to metal powders. However, this method requires an additional process to expose and distribute the carbon nanotubes, rendering the process overly complicated.
Further, Japanese patent laid-open publication No. 2000-223004 discloses a method for exposing the carbon nanotubes in which carbon and the metal particulate are mixed and compacted, then the compacted mixture is cut and selectively etched. However, this method is also substantially too complicated and is difficult to be applied to a field emission device of an electron emission array.
Moreover, Japanese patent laid-open publication No. 2000-36243 discloses a method in which a laser beam is irradiated on the surface of a printed pattern in which carbon nanotubes are covered with silver particles combined with a binder, and the silver particles and the binder present on the surface are selectively removed, so that the carbon nanotubes are exposed. However, the method has a concern in that the carbon nanotubes get thermally damaged by the laser irradiation.